1. Technical Field
This invention relates to an optical disc whose label surface is printable or writable with a water-based ink pen or an ink jet printer and a printable material.
2. Background Art
It is sometimes desired to write or print personal memorandums on a label surface of optical discs as typified by write-once compact discs (CD-R). In general, such optical discs have a protective coat formed of a radiation-cured resin which is repellent to water-based ink. It is then impossible to write or print characters on the protective coat surface with a water-based ink pen or ink jet printer.
It is then a common practice to print with oil-based ink or to attach a label to the disc on which characters are printed. The printing with oil-based ink must be manual writing. The attachment of a label can adversely affect not only the outer appearance, but also subsequent recording and readout operation.
Japanese Patent Application Kokai (JP-A) No. 60432/1994 discloses an optical information medium (compact disc) wherein a hydrophilic resin film is formed on a protective coat surface to provide a hydrophilic surface capable of fixing aqueous printing ink. It is described that the film surface ensures effective printing of characters and solid marks when printed by means of an ink jet printer.
Also Japanese Patent Publication (JP-B) No. 65036/1988 discloses a printable material for ink jet printing comprising a coating layer containing a particulate filler and a binder. The filler particles have a mean particle size of 3 to 25 .mu.m and exposed at the coating layer surface in a distribution of 10,000 to 100,000 particles per square millimeters. JP-A 41585/1986 discloses a printable material for ink jet printing comprising an ink receptive layer consisting of polyvinyl pyrrolidone (PVP) and polyvinyl alcohol (PVA) in a weight ratio of from 1:3 to 5:1. JP-A 63474/1986 discloses a printable material for ink jet printing comprising an ink receptive layer consisting of a copolymer of vinyl pyrrolidone and vinyl acetate. Allegedly these printable materials are printable with clear images.
It is sometimes desired to rewrite the printed characters (or marks) where the contents have been wrong due to misunderstanding or miswriting or for some other reasons. It is convenient if the printed characters can be erased or corrected. However, since conventional water-based ink receptive coatings were developed to improve fixation of printed characters, it was impossible to erase or correct the once printed characters.